Stamped metal toroidal hybrid gas generator

ABSTRACT

A hybrid inflator comprises a housing formed of welded-together metal stampings defining a toroidal gas chamber surrounding a center tie and storing pressurized gas therein. The center tie has a generally cylindrical sidewall and an outlet wall at an upper end thereof defines a rupturably sealed outlet orifice. An inverted stamped metal cup is matingly received in the center tie. The lip of the cup is welded to the lower end of the center tie, and the cup sidewall is circumferentially grooved for separating a sliding piston portion under pressure. A squib support wall and squib closes the lower end of the center tie and inverted cup to define a combustion chamber containing a pyrotechnic gas generant which, upon ignition, causes the inverted cup to separate at the groove and drive the sliding piston upwardly to an open position uncovering inlet openings from the combustion chamber to the gas storage chamber. Hot gasses from the combustion chamber flow into the gas storage chamber and the outlet orifice rupturably opens permitting stored gas and combustion products to exit the inflator. The sliding piston and center tie are tapered to control movement of the piston by friction and deformation, together with lanced limit stop tabs. The cup has a convex bottom, deformation portions and may carry a lance to open the orifice. A baffle provides a surface on which incomplete products of combustion are collected and captures debris. A deformable outlet diffuser provides compact packaging.

This application is a divisional application of application Ser. No.08/321,786 filed on Oct. 12, 1994, now Pat. No. 5,516,147.

FIELD OF INVENTION

The invention herein relates to a compact hybrid inflator for vehicleoccupant restraint systems, in which the inflator housing is made ofstamped metal parts including a breakaway sliding piston.

BACKGROUND OF INVENTION

Hybrid inflators for vehicle occupant restraint systems utilize acombination of stored inert gas and the products of combustion ofpyrotechnic material to deploy an airbag. The inert gas is stored in achamber at a relatively high pressure on the order of 2,000 to 4,000pounds per square inch. The pressure chamber is adjacent to a combustionchamber that contains an initiator and a pyrotechnic material forproducing hot combustion gasses which are delivered to the stored inertgas. The mixture of the hot combustion gasses and stored inert gassesare delivered through an outlet to inflate the airbag of the occupantrestraint system.

Hybrid inflators are particularly useful in that no Azide is required inthe inflation system, and that complex filters are not required to cooland clean the gasses.

The housings of hybrid inflators are generally fabricated of machinedand/or forged metal parts and numerous configurations are provided inthe art for delivering the hot combustion gasses of the pyrotechnicmaterial to the gas storage chamber, and for opening an outlet passageof the housing for inflating the airbag. Examples of such structures areshown in Vancil U.S. Pat. No. 3,788,667, Grosch et al. U.S. Pat. No.3,797,853, Grosch et al. U.S. Pat. No. 3,836,170, Merrell U.S. Pat. No.3,856,180, Merrell U.S. Pat. No. 3,856,181, Johnson U.S. Pat. No.3,868,124, Merrell U.S. Pat. No. 3,869,143, Zeigler U.S. Pat. No.3,865,273, Smith et al. U.S. Pat. No. 3,944,249, Meacham U.S. Pat. No.3,948,540, Goetz U.S. Pat. No. 3,960,390, Marlow U.S. Pat. No.3,966,225, Roth U.S. Pat. No. 3,966,226, Hay U.S. Pat. No. 3,968,980,Woods et al. U.S. Pat. No. 5,076,607 and Frantom U.S. Pat. No.5,199,740.

Because the inflators in the foregoing patents, and particularly theones which are toroidal in configuration, comprise machined and/orforged parts, they are accordingly complex in the number of parts andassembly, and high in cost. Given the widespread use of inflators, thereis a corresponding need to reduce the complexity and cost thereof, aswell as the size and weight without sacrificing efficient operation andreliability.

SUMMARY OF THE INVENTION

Accordingly, it is a principal object of the invention herein to providea hybrid inflator for vehicle occupant restraint systems which isefficient and reliable in operation.

It is an additional object of the invention herein to provide a hybridinflator which is compact and low in weight.

It is a further object of the invention herein to provide a hybridinflator of low complexity with respect to the configuration of itsparts and attendant low cost of manufacture.

It is an additional object of the invention herein to provide a hybridinflator having a housing made of stamped metal parts.

In accomplishing these and other objects of the invention herein, thereis provided a hybrid inflator having a generally toroidal housing formedof welded-together metal stamped parts, the housing defining a storedgas chamber surrounding a center tie, and the gas chamber storing apressurized inert gas. The center tie has a generally cylindricalsidewall and an outlet wall at the upper end thereof, the outlet walldefining a rupturably sealed outlet orifice. An igniter assemblyincluding a pyrotechnic gas generant and squib initiator are mounted inthe center tie with appropriate passages for delivering hot gasses tothe stored gas and a mix of hot and stored gas to the airbag. Accordingto one aspect of the invention, the igniter assembly includes aninverted stamped metal cup having a generally cylindrical sidewallmatingly received in the generally cylindrical sidewall of the centertie. The metal cup has an end wall extending across the center tie todefine, together with an upper portion of the center tie sidewall andthe outlet wall, an outlet cavity adjacent the outlet orifice. Theinverted cup also has a lip adjacent its open end secured to the lowerend of the center tie, and the sidewall of the inverted cup adjacent thelip has a circumferential groove to provide for separation of the cupfrom the lip. A squib support wall closes the lower end of the centertie and inverted cup to define a combustion chamber cavity within theinverted cup. The pyrotechnic gas generant material is provided withinthe combustion chamber and the squib support wall mounts a squib forigniting it.

Upon ignition of the pyrotechnic gas generant material, the expandingcombustion products including hot gasses cause the inverted cup toseparate at the circumferential groove and drive the separated invertedcup upwardly in the center tie to an open position. The center tiedefines at least one inlet opening from the combustion chamber to thegas chamber, and this inlet opening is positioned to be exposed for aflow of combustion products into the stored gas chamber when theinverted cup is driven to its open position. The combustion productsincluding hot gas flow into the gas chamber to heat and thereby increasethe pressure of the stored gas therein. The center tie also defines atleast one outlet opening from the gas chamber to the outlet cavity,which opening remains unblocked by the inverted cup in its open positionand thereby provide a flow path to the outlet orifice. The sealed outletorifice rupturably opens after ignition of the pyrotechnic gas generantmaterial, permitting stored gas and hot combustion gasses to exit theinflator through the outlet opening in the center tie wall, the outletcavity and the outlet orifice.

According to one aspect of the invention, the outlet orifice is sealedby a diaphragm which ruptures upon increased pressure within thehousing. According to another aspect of the invention, the rupturablysealed outlet orifice is opened by a lance extending from the invertedcup and driven through the orifice by the upward sliding motion of theinverted cup.

According to further aspects of the invention, the generally cylindricalcenter tie wall and the inverted cup have surfaces which taper inwardlyin the direction of cup movement, wherein friction and deformation ofthe inverted cup occur as it slides upwardly limit the speed and extentof its upward travel. Additionally, the center tie wall in the outletcavity above the inverted cup has inwardly lanced tabs which provide amechanical limit stop for the inverted cup.

Another particular aspect of the invention is in providing a diffuserover the outlet orifice, and advantageously the diffuser is formed of astamped metal part fitted snugly against the outlet orifice anddeformable away from the outlet orifice by the inflation gasses exitingthe inflator housing. The deformable diffuser provides a more compactinflator prior to operation, and also absorbs some of the energy fromthe initial surge of gas to provide a controlled initial inflation ofthe airbag.

According to another aspect of the invention herein, a baffle isincluded within the housing juxtaposed the outlet opening from thepyrotechnic generant chamber, the baffle receiving and condensing orplating thereon incomplete products of combustion and thus reducing theamount of particles which are undesirable in the stream of inflationgasses.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,its operating advantages and specific objects attained by its use,reference is made to the accompanying drawings and descriptive matter inwhich preferred embodiments of the invention are illustrated.

DRAWINGS

FIG. 1 is a perspective view of a hybrid inflator according to theinvention herein;

FIG. 2 is a cross-sectional view of the hybrid inflator of FIG. 1;

FIG. 3 is a cross-sectional view of the hybrid inflator of FIG. 1 shownoperationally delivering inflation gas;

FIG. 4 is a cross-sectional view of another embodiment of a hybridinflator according to the invention herein; and

FIG. 5 is a cross-sectional view of the hybrid inflator of FIG. 4, shownoperationally delivering inflation gas.

The same reference numerals refer to the same elements throughout thevarious figures.

DESCRIPTION OF PREFERRED EMBODIMENTS

A hybrid inflator 10 according to the invention herein is shown inperspective view in FIG. 1 and in cross-sectional views in its assembledand operating conditions in FIGS. 2 and 3, respectively. The hybridinflator 10 comprises a housing 12 formed of welded-together, stampedmetal parts and including a mounting flange 14. A deformable diffuser 6secured to the upper portion of the housing 12. The term "upper" as usedherein refers to the diffuser side of the hybrid inflator and to theinflator as shown in the drawings, although the hybrid inflator may bemounted in a vehicle in a different orientation. When installed in avehicle, an airbag (not shown in the drawings) is fitted over thediffuser and inflation gasses from diffuser exit openings 18 inflate theairbag.

The housing 12 defines a generally toroidal gas storage chamber 20surrounding a center tie 22. The housing is formed of upper and lowerstamped housing parts 24 and 26, respectively. The upper housing part 24has an upper wall 28 forming the top of the gas storage chamber 20, thewall 28 integrally curving to a depending cylindrical sidewall 30. Themounting flange 14 is also formed integrally with the upper housing part24, extending outwardly from the sidewall 30. The mounting flange mayalso be formed as an extension of the diffuser 16, or provided as aseparate piece. The upper wall 28 includes a central opening receivingthe upper end of the center tie 22, as more fully discussed below.

The lower housing part 26 includes a bottom wall 32 which curves to joina cylindrical sidewall 34, the upper portion of which fits inside thecylindrical sidewall 30 of the upper housing part 24. These parts arewelded together, as indicated at 36. The generally cylindrical centertie 22 is integral with the lower housing part 26, and extends upwardlyfrom the bottom wall 32 to be received in the opening defined in theupper wall 28, where the center tie 22 and upper wall 28 are weldedtogether as indicated at 37. The housing 12 further includes an outletwall 38 extending across the top of center tie 22 and the opening in theupper wall 28, and defining an outlet orifice 40. Thus, the housing 12is fabricated of only two stamped metal parts. A metal diaphragm 41rupturably seals the outlet orifice

An igniter assembly 43 comprises an inverted stamped metal cup 42matingly received within the center tie 22, the inverted cup 42including a sidewall 44 which fits closely within the sidewall of thecenter tie 22. Both the sidewall of the center tie and the sidewall ofthe cup are tapered at a five degree angle toward the outlet wall 38,the taper angle being shown at A in FIG. 2. The inverted cup has aconvex bottom 46, which is joined with the sidewall 44 by a roundedtransition portion 48.

The inverted cup has a lip 50 adjacent its open end, and the lip 50 iswelded to the lower housing part 26 at the transition between the bottomwall and center tie 22, the weld being shown at 52. The lip 50 isseparated from the sidewall 44 of the cup by a circumferential groove 54which weakens the cup and predisposes its separation during operation ofthe inflator, as more fully discussed below. The center tie defines aplurality of inlet openings. 55 to the stored gas chamber, the inletopenings being positioned adjacent and just above the groove 54.

An outlet cavity 56 is defined within the center tie 22 above theinverted cup 42. The outlet cavity 56 communicates with the gas storagechamber 20 through openings 58 formed in the center tie sidewall. Thesidewall of the center tie is also provided with a plurality of lancedtabs 60 which extend inwardly and provide stops for upward movement ofthe inverted cup, as also more fully discussed below. The welds securingthe upper and lower housing parts together and securing the lip 50 ofthe inverted cup to the lower housing part, together with the rupturablediaphragm 41, provide a sealed chamber in which inert gas is storedunder pressure. The gas is preferably argon or nitrogen under pressureof 2,000 to 4,000 pounds per square inch. The gas is loaded through afill port sealed by a weld 59.

The igniter assembly 43 further comprises a stamped metal squib supportwall 62 situated across the open end of the inverted cup, and welded orotherwise secured to the lip 50 of the inverted cup at 63. The squibsupport wall 62 defines a central opening which receives and supports aninitiator 64, also known as a squib. The squib is held in position onthe squib support wall 62 by a thin retainer member 66 which is spotwelded to the squib support wall.

The inverted cup 42, the squib support wall 62 and the squib 64supported thereby together define a combustion chamber 68, in which apyrotechnic gas generant material 70 is contained. Boron potassiumnitrate (BKNO₃) is a satisfactory pyrotechnic for use in the igniterassembly 43 of hybrid inflator 10. A connector retention plate 72 iswelded, at 74, to the bottom wall 32 of the housing 12. The connectorplate 72 defines a central opening 76 which receives and supports a plugconnector, not shown, inserted over the leads 78 of the squib. Theconnector retention plate provides additional rigidity and support tothe housing structure, and also supports the plug connector without needof a full mating recess to receive it.

The hybrid inflator 10 further comprises the diffuser 16 having a toppanel 80 which, upon assembly and prior to operation of the inflator,lies closely adjacent the upper wall 28 and outlet wall 38 of thehousing 12. The diffuser 16 further comprises a cylindrical sidewall 82which is welded to the upper housing part 24 at 84. The sidewall 82defines the diffuser outlet openings 18, and a screen 86 is preferablypositioned within the diffuser covering the openings 18 to preventdebris from entering the airbag during the inflation process.

The operation of the hybrid inflator 10 is illustrated in FIG. 3. Inresponse to a signal indicative of a vehicle crash, a control signal iscommunicated to the squib leads 78, thereby activating the squib 64 toignite the pyrotechnic gas generant material 70. As pressure in thecombustion chamber 68 rises, and exceeds the pressure of the stored gasexerted on the convex bottom wall 46 of the inverted cup, the invertedcup severs at the groove 54. The severed portion of the cup then becomesa sliding piston 45 which is driven upwardly within the center tie 22.The upward movement of the sliding piston portion 45 of the inverted cupis controlled by the taper of the cup and the center tie wall as well asby the friction between these parts. Both of these factors operate toslow or stop the sliding piston portion 45 of the inverted cup after ithas moved far enough to expose the inlet openings 55, providing an entrypassage for the hot burning gasses to the gas storage chamber. Acomplete stop of the sliding piston 45 is insured by the inwardlyprotruding lanced tabs 60, in the position shown in FIG. 3. The convexbottom 46 of the inverted cup 42 reduces the possibility of the bottomblowing out before the cup separates at the groove 54, and thetransition portions 48 of the cup deform as the cup is driven upwardlyin the tapered center tie.

The hot burning gasses enter the gas storage chamber 20 through theinlet openings 55, and heat the stored gas therein. This results in apressure rise in the storage chamber 20 and when the rupture strength ofthe diaphragm 41 is exceeded, the diaphragm ruptures and allows theheated gas to vent through the outlet orifice 40. The momentum andpressure of the escaping gas deforms the diffuser, lifting the top panel80 away from the outlet orifice 40, and creates a path for the gas to bedelivered through the diffuser openings 18. The screen 86 preventsdebris from the inflator, including portions of the ruptured diaphragm41, from being carried into an airbag attached to the inflator. Theorifice 40 throttles the flow of gas from the storage chamber andprovides the proper fill rate into the airbag. The deforming of thediffuser 16 slows down the pressure onset to the airbag by absorbingsome of the energy of the escaping gas, and "softens" the initialinflation of the airbag. Fitting the diffuser in close proximity to thehousing also improves the packaging requirements in using the inflatorfor a driver's side airbag system.

Another hybrid inflator 100 according to the invention herein is shownin its assembled condition in FIG. 4 and its operative condition in FIG.5. The hybrid inflator 100 is similar to the hybrid inflator 10 above,having a housing formed of stamped metal parts and defining a toroidalgas storage chamber 120 surrounding a generally cylindrical center tie122 The housing 112 is fabricated of an upper housing part including amounting flange 114, and a lower housing part 126. One distinctionbetween the hybrid inflator 100 and the hybrid inflator 10 describedabove is that the upper housing part 124 includes the top wall 138 ofthe outlet cavity 156 and defines the outlet orifice 140 therefrom, andthe lower housing part 126 includes the tapered sidewall of the centertie 122 which is welded at its upper end to the upper housing 124, theweld being indicated at 137. This demonstrates the flexibility in designavailable in providing an inflator of stamped metal parts.

The hybrid inflator 100 comprises an igniter assembly 143, and isprovided with a lance 110 mounted to and extending from the convexbottom 146 of inverted cup 144 toward metal diaphragm 141 covering theoutlet orifice 140.

The inverted cup 144 has a lower lip 150 separated from a sliding pistonportion 145 by a circumferential groove 152. The lip 150 is welded to amachined squib holder 148 fitted into the lower portion of the center122 and welded to the lower housing part 126, at 128. The squib holder148 mounts squib 164 and defines a recess 166 for a plug connector tothe squib leads 168.

Another distinction of the hybrid inflator 100 is a rigid diffuser 116welded to the top wall 138 and including a top panel 117 and a sidewall118 defining radial exit ports 119.

In the assembled, pre-operational condition shown in FIG. 4, the lance110 has its tip adjacent the metal diaphragm 141, and as the invertedcup is driven upward to the operative position shown in FIG. 5, thelance 110 mechanically pierces the diaphragm 141. This allows stored gasto exit the outlet orifice 140 and diffuser prior to any substantialheating and expanding of the stored gasses by the ignited pyrotechnicmaterial, and thereby softens the onset of pressure applied to theairbag. The rigid diffuser provides a clear path to the airbag for thesofter onset of pressurized inflation gas.

The hybrid inflator 100 is further equipped with an internal baffle 190extending upwardly from the bottom wall of the lower housing part 126,generally surrounding the inlet openings 155 from the combustion chamberand in the path of the exiting products of combustion. When thepyrotechnic gas generant material is ignited and the sliding pistonportion 145 of cup 144 separates from its lip 150 and moves upwardly toexpose inlet openings 155, some particulates and incomplete products ofcombustion exit he openings and impinge on the baffle 190. Some of thoseparticles and incomplete products of combustion plate onto the baffle,and others are deflected downwardly by the baffle, away from the gasflow to the outlet openings 158 leading to the outlet cavity 156. Thebaffle includes a base portion 191 which conforms to and is used tomount the baffle within the lower housing part 126. This may beaccomplished by spot welds, in that no sealing function is required.

The hybrid inflator 100 operates similarly to the hybrid inflator 10described above, with the exception that the metal diaphragm coveringthe outlet orifice is ruptured earlier in the inflation cycle and theinflation gas flows through a rigid diffuser, as noted in the precedingparagraphs. Further, the baffle 190 assists in reducing any particleswhich might otherwise be included in the outlet flow.

Accordingly, preferred embodiments of hybrid inflators have beendescribed which admirably achieve the objects of the invention herein.With reference to the description of the preferred embodiments, thoseskilled in the art will appreciate that modifications may be madewithout departing from the spirit of the invention. Therefore, it is notintended that the scope of the invention be limited to the specificembodiments illustrated and described. Rather, it is intended that thescope of the invention be determined by the appended claims andequivalents thereof.

We claim:
 1. A hybrid inflator comprising a housing having:A) an upperstamped metal housing part including a top wall and a cylindricalsidewall depending therefrom; B) a lower stamped metal housing partincluding a bottom wall, a cylindrical sidewall extending upwardlytherefrom and engaged with the cylindrical sidewall of the upper housingpart and welded thereto, and a generally cylindrical center tieintegrally formed in one piece with the bottom wall and extending fromthe bottom wall to the top wall and welded to the top wall; C) an upperwall integrally formed in one piece with one of the upper or lowerhousing parts and extending across the upper end of the center tie; D)the housing defining a gas storage chamber surrounding the center tieand the center tie defining at least one inlet opening to the gasstorage chamber and the housing further defining a rupturably sealedoutlet orifice from the gas storage chamber; and E) an igniter assemblymounted in the center tie and including a pyrotechnic gas generantmaterial for producing and delivering hot gasses to the gas storagechamber through the inlet opening thereto.
 2. A hybrid inflator asdefined in claim 1 wherein the upper wall defines the rupturably sealedexit orifice from the housing, and the upper wall, center tie andigniter assembly defines an outlet cavity adjacent the exit orifice,theoutlet cavity communicating with the stored gas chamber through at leastone outlet opening defined by the center tie.
 3. A hybrid inflator asdefined in claim 2 wherein the igniter assembly further comprises astamped metal squib holder secured across the lower end of the centertie and a squib mounted therein, the igniter assembly including thesquib holder and squib defining a combustion chamber for the pyrotechnicgas generant material.
 4. A hybrid inflator as defined in claim 3 andfurther comprising a bottom plate secured to the bottom wall of thehousing and extending acros the lower end of the center tie, the bottomplate defining an opening for ebracing and supporting a plug connter forproviding an initiator signal to the squib.
 5. A hybrid inflator asdefined in claim 1 wherein the housing further comprises a mountingflange integral with one of the upper or lower stamped metal housingparts.
 6. A hybrid inflator as defined in claim 1 and further comprisinga stamped metal deformable diffuser including a top panel and acylindrical diffuser sidewall, the cylindrical diffuser sidewall securedto the cylindrical sidewall of the upper housing part with the top panellying closely adjacent the top wall and outlet orifice of the housing,and the top panel being deformable away from the top wall of the housingby inflation gasses from the exit orifice, the diffuser sidewalldefining outlet openings for delivering the inflation gas to an airbag.7. A hybrid inflator as defined in claim 1 wherein the igniter assemblyfurther comprises a stamped metal squib holder secured across the openend of the center tie, and a squib mounted therein, the igniter assemblyincluding the squib holder and together defining a combustion chamberfor the pyrotechnic gas generant material.
 8. A hybrid inflator asdefined in claim 1 and further comprising a baffle secured to thehousing within the gas storage chamber and positioned to receiveincomplete combustion products and debris delivered to the gas storagechamber through the at least one inlet opening from the igniterassembly, said baffle angled to deflect debris away from the outletorifice and the path of gas flow leading to the outlet orifice.
 9. Ahybrid inflator as defined in claim 8 wherein the center tie defines aplurality of inlet openings thereabout and the baffle is positionedsurrounding the center tie.
 10. A hybrid inflator as defined in claim 9wherein the baffle is a stamped metal part welded to the lower housingpart.